The first stage of cell respiration is ___ , the breakdown of ___
to form two molecules of ___
. The resulting molecules may pass through several different pathways, depending on the organism in question. In some organisms, such as yeast,___
occurs. In other organisms, aerobic respiration occurs.

Glycolysis porduces
molecules of NADH and
molecules of ATP (net gain).

In an intermediate stage, pyruvic acid is converted into
. This process produces
molecules of NADH (per glucose molecule).

The Krebs cycle takes acetyl CoA and completely oxidizes it to
. In the process,
molecules of ATP are gained. This process also produces
moecules of NADH and
molecules FADH2. (All of these values are per glucose molecule.)

The
is a system of electron carriers embedded into the inner membrane of the mitochondria. The compounds act to accept energy bearing electrons from
and
and transfer them step-by-step to free
, which is reduced by these electrons combining with hydrogen to form
.